This is a study to determine methods for the preservation of corneal tissue suitable for penetrating keratoplasty. We have developed a method for the long term preservation which involves the ultimate storage of isolated corneas in liquid nitrogen. The procedure is exacting and involves the use of equipment that is often not available in small hospitals or in foreign countries. We are trying to develop methods which will preserve corneas for intermediate times and be more widely useful. Of the many methods investigated, two have shown promising results. One method involves storage of excised corneas and scleral rims in a dual interface chamber and storage at 4 degrees C. The second involves storage of corneas with scleral rims in a modified tissue culture media (M-K media) also at 4 degrees C. Histological and electron microscopic examination of stored material shows good retention of cellular integrity. Results of human transplants, especially with donor corneas stored in M-K media, for up to 14 days, have been excellent. This study also includes work on trying to accurately define the reason for graft failures and efforts to prevent true rejections.